/*
 * Copyright 2002-2007 the original author or authors.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package jacky.lanlan.song.collection;

import java.util.*;

import jacky.lanlan.song.lang.ArrayUtils;
import jacky.lanlan.song.lang.ObjectUtils;

/**
 * Miscellaneous collection utility methods. Mainly for internal use within the framework.
 * 
 * @author Juergen Hoeller
 * @author Rob Harrop
 * @since 1.1.3
 */
public abstract class CollectionUtils {

	/**
	 * Return <code>true</code> if the supplied Collection is <code>null</code> or empty. Otherwise,
	 * return <code>false</code>.
	 * 
	 * @param collection
	 *          the Collection to check
	 * @return whether the given Collection is empty
	 */
	public static <T> boolean isEmpty(Collection<T> collection) {
		return (collection == null || collection.isEmpty());
	}

	/**
	 * Return <code>true</code> if the supplied Map is <code>null</code> or empty. Otherwise, return
	 * <code>false</code>.
	 * 
	 * @param map
	 *          the Map to check
	 * @return whether the given Map is empty
	 */
	public static <K, V> boolean isEmpty(Map<K, V> map) {
		return (map == null || map.isEmpty());
	}

	/**
	 * Convert the supplied array into a List. A primitive array gets converted into a List of the
	 * appropriate wrapper type.
	 * <p>
	 * A <code>null</code> source value will be converted to an empty List.
	 * 
	 * @param source
	 *          the (potentially primitive) array
	 * @return the converted List result
	 * @see ObjectUtils#toObjectArray(Object)
	 */
	public static List<?> arrayToList(Object source) {
		return Arrays.asList(ObjectUtils.toObjectArray(source));
	}

	/**
	 * Merge the given array into the given Collection.
	 * 
	 * @param array
	 *          the array to merge (may be <code>null</code>)
	 * @param collection
	 *          the target Collection to merge the array into
	 */
	public static void mergeArrayIntoCollection(Object array, Collection collection) {
		if (collection == null) { throw new IllegalArgumentException("Collection must not be null"); }
		Object[] arr = ObjectUtils.toObjectArray(array);
		for (int i = 0; i < arr.length; i++) {
			collection.add(arr[i]);
		}
	}

	/**
	 * Merge the given Properties instance into the given Map, copying all properties (key-value
	 * pairs) over.
	 * <p>
	 * Uses <code>Properties.propertyNames()</code> to even catch default properties linked into the
	 * original Properties instance.
	 * 
	 * @param props
	 *          the Properties instance to merge (may be <code>null</code>)
	 * @param map
	 *          the target Map to merge the properties into
	 */
	public static void mergePropertiesIntoMap(Properties props, Map<String, String> map) {
		if (map == null) { throw new IllegalArgumentException("Map must not be null"); }
		if (props != null) {
			for (Enumeration<?> en = props.propertyNames(); en.hasMoreElements();) {
				String key = (String) en.nextElement();
				map.put(key, props.getProperty(key));
			}
		}
	}

	/**
	 * Check whether the given Iterator contains the given element.
	 * 
	 * @param iterator
	 *          the Iterator to check
	 * @param element
	 *          the element to look for
	 * @return <code>true</code> if found, <code>false</code> else
	 */
	public static <T> boolean contains(Iterator<T> iterator, T element) {
		if (iterator != null) {
			while (iterator.hasNext()) {
				T candidate = iterator.next();
				if (ObjectUtils.nullSafeEquals(candidate, element)) { return true; }
			}
		}
		return false;
	}

	/**
	 * Check whether the given Enumeration contains the given element.
	 * 
	 * @param enumeration
	 *          the Enumeration to check
	 * @param element
	 *          the element to look for
	 * @return <code>true</code> if found, <code>false</code> else
	 */
	public static <T> boolean contains(Enumeration<T> enumeration, T element) {
		if (enumeration != null) {
			while (enumeration.hasMoreElements()) {
				T candidate = enumeration.nextElement();
				if (ObjectUtils.nullSafeEquals(candidate, element)) { return true; }
			}
		}
		return false;
	}

	/**
	 * Check whether the given Collection contains the given element instance.
	 * <p>
	 * Enforces the given instance to be present, rather than returning <code>true</code> for an equal
	 * element as well.
	 * 
	 * @param collection
	 *          the Collection to check
	 * @param element
	 *          the element to look for
	 * @return <code>true</code> if found, <code>false</code> else
	 */
	public static <T> boolean containsInstance(Collection<T> collection, T element) {
		if (collection != null) {
			for (T candidate : collection) {
				if (candidate == element) { return true; }
			}
		}
		return false;
	}

	/**
	 * Return <code>true</code> if any element in '<code>candidates</code>' is contained in '
	 * <code>source</code>'; otherwise returns <code>false</code>.
	 * 
	 * @param source
	 *          the source Collection
	 * @param candidates
	 *          the candidates to search for
	 * @return whether any of the candidates has been found
	 */
	public static <T> boolean containsAny(Collection<T> source, Collection<? extends T> candidates) {
		if (isEmpty(source) || isEmpty(candidates)) { return false; }
		for (T candidate : candidates) {
			if (source.contains(candidate)) { return true; }
		}
		return false;
	}

	/**
	 * Return the first element in '<code>candidates</code>' that is contained in '<code>source</code>
	 * '. If no element in '<code>candidates</code>' is present in '<code>source</code>' returns
	 * <code>null</code>. Iteration order is {@link Collection} implementation specific.
	 * 
	 * @param source
	 *          the source Collection
	 * @param candidates
	 *          the candidates to search for
	 * @return the first present object, or <code>null</code> if not found
	 */
	public static <T> T findFirstMatch(Collection<T> source, Collection<? extends T> candidates) {
		if (isEmpty(source) || isEmpty(candidates)) { return null; }
		for (T candidate : candidates) {
			if (source.contains(candidate)) { return candidate; }
		}
		return null;
	}

	/**
	 * Find a value of the given type in the given Collection.
	 * 
	 * @param collection
	 *          the Collection to search
	 * @param type
	 *          the type to look for
	 * @return a value of the given type found, or <code>null</code> if none
	 * @throws IllegalArgumentException
	 *           if more than one value of the given type found
	 */
	public static <T> T findValueOfType(Collection<T> collection, Class<?> type) throws IllegalArgumentException {
		if (isEmpty(collection)) { return null; }
		Class<?> typeToUse = (type != null ? type : Object.class);
		T value = null;
		for (T e : collection) {
			if (typeToUse.isInstance(e)) {
				if (value != null) { throw new IllegalArgumentException("More than one value of type [" + typeToUse.getName()
						+ "] found"); }
				value = e;
			}
		}
		return value;
	}

	/**
	 * Find a value of one of the given types in the given Collection: searching the Collection for a
	 * value of the first type, then searching for a value of the second type, etc.
	 * 
	 * @param collection
	 *          the collection to search
	 * @param types
	 *          the types to look for, in prioritized order
	 * @return a of one of the given types found, or <code>null</code> if none
	 * @throws IllegalArgumentException
	 *           if more than one value of the given type found
	 */
	public static <T> T findValueOfType(Collection<T> collection, Class<?>[] types) throws IllegalArgumentException {
		if (isEmpty(collection) || ObjectUtils.isEmpty(types)) { return null; }
		for (int i = 0; i < types.length; i++) {
			T value = findValueOfType(collection, types[i]);
			if (value != null) { return value; }
		}
		return null;
	}

	/**
	 * Determine whether the given Collection only contains a single unique object.
	 * 
	 * @param collection
	 *          the Collection to check
	 * @return <code>true</code> if the collection contains a single reference or multiple references
	 *         to the same instance, <code>false</code> else
	 */
	public static <T> boolean hasUniqueObject(Collection<T> collection) {
		if (isEmpty(collection)) { return false; }
		boolean hasCandidate = false;
		T candidate = null;
		for (T e : collection) {
			if (!hasCandidate) {
				hasCandidate = true;
				candidate = e;
			}
			else if (candidate != e) { return false; }
		}
		return true;
	}

	public static <T> T[] toArray(final Iterator<T> itor, final Class<? extends T[]> newType) {
		List<T> list = toList(itor);
		return ArrayUtils.toArray(list, newType);
	}

	public static <T> List<T> toList(Iterator<T> itor) {
		return toList(itor, 12);
	}

	public static <T> List<T> toList(Iterator<T> itor, int estimatedSize) {
		final List<T> list = new ArrayList<T>(estimatedSize);
		addToList(itor, list);
		return list;
	}

	@SuppressWarnings("unchecked")
	public static void addToList(Iterator itor, List list) {
		while (itor.hasNext()) {
			list.add(itor.next());
		}
	}

}
